Reliable transgene expression in immune effector cells such as T cells can provide needed insight into immunological mechanisms, and would also help enable novel immunotherapeutic strategies such as, e.g., gene therapy approaches for treating cancer as well as immunological, hematological, infectious, and genetic disorders. Unfortunately, however, stable and effective transgene expression in T cells has proven to bean elusive goal, often requiring hit-or-miss experimentation. It is well-established, for example, that transduction of resting primary T lymphocytes with viral vectors, such as retroviral derived vectors, generally results in very low efficiencies [Yamashita and Emerman, J. Virology 2006 Jan. 5; 344(1):88-93]. Accordingly, studies in retroviral-mediated gene transfer to primary T lymphocytes over the past ten years have examined a number of different strategies to improve transduction efficiencies, leaving the even greater hurdle of satisfactory transgene expression as a more distant goal.
With respect to viral systems providing permanent integration into the host cell, it has been shown that T cell activation in conjunction with lentiviral transduction can significantly improve gene delivery to T cells. See, e.g., Unutmaz et al., J Exp Med. 1999 Jun. 7; 189(11):1735-46; Pollock et al., J. Virology, 1998 June; 72(6):4882-92; Costello et al., Gene Ther. 2000 April; 7(7):596-604; Bai et al., Gene Ther. 2003 August; 10(17):1446-57; Lu et al., J Gene Med. 2004 September; 6(9):963-73. Bai et. al. and Lu et. al., for example, independently reported that both phytohemagluttinin (PHA) and anti-CD3/antiCD28 costimulation of T lymphocytes can improve lentiviral gene delivery efficiencies, demonstrating 80 to >99% transduction. Despite these reported successes in transduction efficiency, however, the actual levels of gene expression obtained by these researchers is inconclusive based on the reported data.
Unfortunately, however, attempts to reproduce these results using non-integrative viral systems have been more problematic. See, e.g., Schroers et al., Exp Hematol. 2004 June; 32(6):53646. In the Schroers study, PHA activation provided only a modest improvement in transduction efficiency with adenoviral vectors, approaching only 45 percent transduction, significantly lower than that obtained using lentiviral vectors. Thus, there remains a significant need in the art for improved methods and compositions capable of high transgene expression in T cells in non-integrative viral systems, e.g., to provide proteins of therapeutic, industrial, or research uses. The present invention addresses this and other needs.